STERLING, Va. (AP) — President Donald Trump on Sunday dangled the prospect of renewing his tariff threat against Mexico if the U.S. ally doesn’t cooperate on border issues, while some of his Democratic challengers for the White House said the last-minute deal to avert trade penalties was overblown.

In a series of tweets, Trump defended the agreement heading off the 5% tax on all Mexican goods that he had threatened to impose Monday, but he warned Mexico that, “if for some unknown reason” cooperation fails, “we can always go back to our previous, very profitable, position of Tariffs.”

Still, he said he didn’t believe that would be necessary.

The tweets came amid questions about just how much of the deal — announced with great fanfare Friday — was really new. It included a commitment from Mexico, for instance, to deploy its new National Guard to its southern border with Guatemala. Mexico, however, had already intended to do that before Trump’s latest threat and had made that clear to U.S. officials. Mexican officials have described their commitment as an accelerated deployment.

The U.S. also hailed Mexico’s agreement to embrace the expansion of a program implemented earlier this year under which some asylum-seekers are returned to Mexico as they wait out their cases. But U.S. officials had already been working to expand the program, which has led to the return of about 10,000 people to Mexico, without Mexico’s public embrace.

“The president has completely overblown what he reports to have achieved. These are agreements that Mexico had already made, in some cases months ago,” said Democratic presidential candidate Beto O’Rourke, speaking on ABC’s “This Week.” ”They might have accelerated the time table, but by and large the president achieved nothing except to jeopardize the most important trading relationship that the United States of America has.”

Another 2020 candidate, Sen. Bernie Sanders of Vermont, chastised Trump for using tariffs as a threat and operating a “trade policy based on tweets.”

“I think what the world is tired of and what I am tired of is a president who consistently goes to war, verbal war with our allies, whether it is Mexico, whether it is Canada,” he said.

But acting Homeland Security Secretary Kevin McAleenan, speaking on “Fox News Sunday,” insisted “all of it is new,” including the agreement to dispatch around 6,000 National Guard troops.

“This is the first time we’ve heard anything like this kind of number of law enforcement being deployed in Mexico to address migration, not just at the southern border but also on the transportation routes to the northern border and in coordinated patrols in key areas along our southwest border,” he said, adding that “people can disagree with the tactics” but “Mexico came to the table with real proposals” that will be effective, if implemented.

Trump echoed the same in his tweets, insisting the deal was being misrepresented.

“We have been trying to get some of these Border Actions for a long time, as have other administrations, but were not able to get them, or get them in full, until our signed agreement with Mexico,” he wrote. “Mexico was not being cooperative on the Border in things we had, or didn’t have, and now I have full confidence, especially after speaking to their President yesterday, that they will be very cooperative and want to get the job properly done.”

He also teased the idea that more was agreed to than was announced Friday, saying that “some things” and “one in particular” had been left out of the release but would be “announced at the appropriate time.”

He could have been referring to discussion about Mexico becoming a “safe third country,” which would make it harder for asylum-seekers who pass through the country to claim refuge in the U.S. The idea, which Mexico has long opposed, was discussed during negotiations. But Mexican Foreign Minister Marcelo Ebrard has said Mexico did not agree to it.

Mexico’s ambassador in Washington nonetheless said her country is committed to working with the U.S. and that discussions will continue.

“We want to continue to work with the U.S. very closely on the different challenges that we have together. And one urgent one at this moment is immigration,” said Martha Barcena. She told CBS’ “Face the Nation” that the countries’ “joint declaration of principles … gives us the base for the road map that we have to follow in the incoming months on immigration and cooperation on asylum issues and development in Central America.”

She said the U.S. wants to see the number of migrants crossing the border return to levels seen in 2018.